Much information has been published on the components of the electron transport chain but there are obvious ambiguities and uncertainties in the reported findings. The molecular properties of cytochrome c oxidase are, probably, the most controversial. Subunits ranging from two to nine have been reported. Cytochrome c oxidase has been purified mainly by solubilization with detergent and repeated precipitations with ammonium. In this investigation we propose to couple solubilization and ammonium sulfate fractionation, with simple conventional chromatography on DEAE- cellulose, hydroxylapatite and gel filtration in order to purify the enzyme to homogeneity. This preparation will be the starting material for elucidating the molecular properties of the enzyme. Our long term objective is to examine the properties of the enzyme which might be suggestive of regulation and control of cellular energy metabolism and to explore the mechanism of the transduction of energy for cellular synthesis of ATP. The electron transport system is vital to the organism. It is the mechanism for the perpetuation of cellular metabolic activities and the concomitant production of energy. Another aspect of this proposal is to study the biochemistry of the interactions of common drugs, immunosuppressive agents and cancer chemotherapeutic agents, with the enzymes in the catabolic sequence of purine nucleotide metabolism. The study hopes to provide an awareness of the secondary effects of chemotherapeutic agents on mammalian enzymes. As a long term goal, these studies will provide for students practice of the principles of basic laboratory techniques for research in enzymology.